Nikki Haley will resign from her job as ambassador to the United Nations at the end of the year, she announced Tuesday in a press conference with President Trump. Prior to her appointment in November 2016, Haley was the first female governor of South Carolina.

Haley told reporters that she does not plan to run in 2020.

Scott Pruitt

For months, pressure was mounting against Environmental Protection Agency Administrator Scott Pruitt because of several allegations of ethics violations. On July 5, 2018, Trump tweeted that he had accepted Pruitt's resignation.

The president said Pruitt did an "outstanding job" and "he would always be thankful to him for this." Andrew Wheeler was tapped as Pruitt's replacement.

Omarosa Manigault NewmanThe White House says Omarosa Manigault Newman - director of communications for the White House Office of Public Liaison - left the administration in early 2018. The White House aide was initially known as a reality television star, beginning with the first season of "The Apprentice." She is among several aides expected to leave the administration following Trump's first year in office.

Thomas Bossert

White House press secretary Sarah Sanders said in a statement regarding the Homeland Security adviser's resignation: "The President is grateful for Tom's commitment to the safety and security of our great country. Tom led the White House's efforts to protect the homeland from terrorist threats, strengthen our cyber defenses, and respond to an unprecedented series of natural disasters. President Trump thanks him for his patriotic service and wishes him well."

David ShulkinVeterans Affairs Secretary David Shulkin, a lone holdover from the Obama Administration, left his position following an internal investigation alleging ethics violations and misuse of taxpayer dollars. Shulkin claims he resigned from his position, while the White House says he was fired.

H.R. McMasterNational security advisor Gen. H.R. McMaster is set to be replaced in April by former U.N. Ambassador John Bolton. McMaster was appointed in February 2017 after Trump fired Lt. Gen. Michael Flynn. McMaster faced long-running tension with President Donald Trump in part over his style and disposition in Oval Office briefings, ABC News reported.

Andrew McCabeOn March 16, the president tweeted that Andrew McCabe, deputy director of the FBI, had been fired. He called it a "great day for the hard working men and women of the FBI." McCabe, who was fired just two days before his retirement, kept memos of his conversations with the president much like his former boss James Comey, ABC News reported.

Rex TillersonSecretary of State Rex Tillerson has left the administration and been replaced by former CIA director Mike Pompeo, the president announced on Twitter on March 13. Trump nominated then-CIA deputy director Gina Haspel to replace Pompeo.

Gary CohnWhite House chief economic adviser Gary Cohn resigned from his post in early March 2018 following a high-profile battle over tariffs the president wants to impose on steel and aluminum imports.

Hope Hicks Hicks was the longest serving Trump aide before she announced her resignation as White House communications director. Trump praised Hicks for her work over the last three years, saying that he "will miss having her by my side."

The resignation came after Hicks admitted to occasionally telling "white lies" for Trump while being interviewed by the House intelligence panel. She said she had not lied about anything relevant to the Russia investigation.

Tom PriceFormer Health and Human Services Secretary Tom Price resigned amidst criticism of his use of private planes for government travel. Price's departure came as he was being investigated by the inspector general's office at the U.S. Department of Health and Human Services.

Steve BannonBannon served as the White House's chief strategist before resigning from his post on August 14, exactly one year after he joined Trump's campaign. He returned to leading the conservative media outlet Breitbart News following his resignation.

Sean SpicerThe White House press secretary resigned after a tumultuous six-month run on the podium where he often had run-ins with the press. His daily televised briefings made him the subject of a high-profile Saturday Night Live parody by Melissa McCarthy.

Michael FlynnTrump's first National Security Advisor, former Lieutenant General Michael Flynn, had the shortest tenure in that position. After just 24 days, Flynn resigned on February 13, after The Washington Post stated he had spoken with Russian Ambassador Sergey Kislyak during the transition of power.

James ComeyTrump fired the FBI director on May 9, 3-and-a-half years into a 10-year term. He initially claimed that Comey's firing was due to his handling of the Hillary Clinton investigation during the 2016 election, but he also admitted to NBC's Lester Holt that it was because he was unhappy with the investigation into his own campaign's ties with Russia.

Reince Priebus

Former RNC chair Reince Priebus was appointed to the powerful position of Chief of Staff but unceremoniously fired, seemingly via tweet, on July 28. Trump announced that General John Kelly, serving as Secretary of Homeland Security, would be replacing him.

I am pleased to inform you that I have just named General/Secretary John F Kelly as White House Chief of Staff. He is a Great American....

Sally YatesActing Attorney General Sally Yates was fired just hours after she announced the Justice Department would not defend Trump's controversial executive order temporarily banning all refugees and travelers from certain countries.